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Pacifier protection Newborn babies that use dummies may have better protection against cot death because it improves their cardiac control, Australian research shows.

Associate Professor Rosemary Horne, of the Monash Institute of Medical Research says epidemiological studies have consistently shown dummy use protects against Sudden Infant Death Syndrome (SIDS).

However, she says, how the soother does this has been unclear.

"Since 2005 there have been a number of case-controlled studies and they have all shown dummies to be protective, yet how does it work when dummies fall out 15 minutes after the baby goes to sleep," she asks.

In research presented at the Pediatric Academic Societies annual meeting in the US, Horne and colleagues suggest the use of dummies helps improve infants' cardiac control.

Horne says SIDS is related to the failure of the infant's cardiac system to adjust appropriately to changes in heart rate and blood pressure and the inability to arouse themselves from sleep when breathing stops or there is a sudden fall in blood pressure.

The dummy therefore has to either increase arousal or improve cardiac control, she says.

"It is counterintuitive that it would increase arousal as you give a dummy to a baby to go to sleep," says Horne.

While her team is also researching dummy impact on arousal, this latest work centres on the device's impact on blood pressure and heart rate.

Sleeping babes

For the research 37 healthy full-term-born infants were monitored during day sleeps at two to four weeks, two to three months and five to six months.

Although all infants routinely slept on their backs at home - the position recommended to prevent SIDS - during the study the infants were placed on their backs and stomachs (prone) to sleep, as the prone position is a major risk for SIDS.

The infants were divided into dummy and non-dummy users and their blood pressure and heart rate variability was measured.

The team found in dummy users, the act of sucking increased heart rate variability, a measure of how the cardiovascular system adjusts the heart rate in response to changes in blood pressure, across all age groups.

However, when dummy users were compared with non-users during non-sucking periods, differences in heart rate variability were only evident in the youngest two to four-week-old age group.

In this age group, dummy users had higher heart rate variability than non-users even when babies weren't sucking.

Horne says this indicates dummy use may improve cardiac control in newborns, which may serve as a protective mechanism for SIDS.

More to the mystery

However she admits the finding does not solve the mystery.

"I don't think heart rate variability is the full story," Horne says. "The biggest risk time for SIDS is at two to three months. If [a dummy] is going to be protective we would think the effect would be most marked at this age and in the prone position."

She says the study shows dummy sucking does have a marked effect on blood pressure and heart rate.

"We are also looking at blood pressure control and the way blood pressure and heart rate work together as a reflex."

Horne says since 2005 the American Academy of Pediatrics has recommended dummy use for all babies once breast feeding is established.

However, she says, SIDS organisations in Australia and New Zealand have been reluctant to follow this lead as the underlying mechanism behind dummy protection was not known.